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Published Date: 2012-06-04 11:31:40
Subject: PRO/AH/EDR> Red tide, fish - Mexico: (OA)
Archive Number: 20120604.1155670

RED TIDE, FISH - MEXICO: (OAXACA)
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Date: Wed 30 May 2012
Source: Ciudadania Express [in Spanish, trans. Mod.PMB, edited]
http://ciudadania-express.com/2012/05/30/estudiaran-muerte-masiva-de-peces-en-chacahua/

A large number of dead fish were found in the past days at the Chachahua lagoon system in the natural reserve located in Tututepec de Melchor Ocampo, Oaxaca. Several institutions carried out coordinated investigations to elucidate the cause of this phenomenon. Their conclusion was that the lack of oxygen caused by the presence of the algae _Cochlodinium polykrikoides_ originated a phenomenon known as "red tide".

According to the State Institute of Ecology and Sustainable Development of Oaxaca, several water and fish samples were collected and analyzed, concluding that the die-off was caused by algal proliferation, affecting principally fingerlings and juveniles.

Even though the phenomenon killed thousands of fish, it did not affect many of the species present at the lagoon, for which fishing activities will not be affected.

Roads and tracks of Oaxaca is building a canal to feed the lagoon system with freshwater, thus diminishing the effect of the algal bloom.

[Byline: Shinji Harper]

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[Red tide or harmful algal blooms are events in which single-celled protists, dinoflagellates, proliferate rapidly and accumulate in the water column. These events are associated with wildlife mortalities, because under certain circumstances these organisms can produce potent toxins. Normally these toxins enter the food web when they are consumed by filter feeding animals, such as clams, oysters, mussels, in which the toxin bioaccumulates. _Cochlodinium polykrikoides_ is a bloom dinoflagellate whose distribution is restricted to warm and tropical waters. Blooms caused by _C. polykrikoides_ have been associated with massive fish kills, and is regarded as a potentially toxic dinoflagellate. Eutrophic environments are very susceptible to harmful algal blooms.

For a picture of the dinoflagellate go to http://images.marinespecies.org/resized/25990_cochlodinium-polykrikoides.jpg.

A map of the affected area can be accessed at http://healthmap.org/r/2vwK. - Mod.PMB]

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